The invention relates to correcting video artifacts caused by interlacing.
With interlaced video a field of pixels for the odd lines are alternately transmitted with a field of pixels for the even lines. This can result in interlaced comb artifacts for an object in the field of view that has moved several pixels between the time that the odd and even fields were recorded. When the fields are combined into a single progressive frame the moving edge of the object can appear comb-like. Even in full-speed progressive motion display this comb-like artifact is visible as a moving jagged edge where a smooth or motion blurred edge would be expected.
In one aspect, the invention features, in general, a method of correcting deinterlaced video by determining whether the deinterlaced video has comb artifact areas, and correcting the comb artifact areas.
In another aspect, the invention features, in general, a method of correcting deinterlaced video by determining whether the deinterlaced video has comb artifact areas by calculating a group value based on differences in pixel values between adjacent rows and the differences in pixel values of alternate rows for pixels in a group of pixels and comparing the group value (which could be a median value of factors determined for each pixel) with a threshold, and correcting the comb artifact areas.
Preferred embodiments of the invention may include one or more of the following features. In preferred embodiments the detection of comb artifacts includes comparing the differences in pixel values between adjacent rows with the differences in pixel values of alternate rows. Comb artifact detection also includes calculating the sum of squared differences between a subject pixel and pixels immediately above and below it, and also includes determining the sum of squared differences between the subject pixel and the pixel two rows above and the pixel two rows below it. The comparison can include determining the ratio of the sum of squared differences between a subject pixel and pixels immediately above and below it, and the sum of squared differences between the subject pixel and the pixel two rows above and the pixel two rows below it. Alternatively the comparison can include determining the difference of the sum of squared differences between a subject pixel and pixels immediately above and below it, and the sum of squared differences between the subject pixel and the pixel two rows above and the pixel two rows below it. The ratio or the difference thus determined can be compared with a predetermined (e.g., threshold) value. The ratios or the differences can also be determined for pixels in a group of pixels surrounding the subject pixel, and the ratios or differences (or a median for the ratios or differences) for the group can be compared with a predetermined (e.g., threshold) value. Alternatively, a pixel increment value can be assigned to each pixel of a group of pixels that has a ratio or difference that exceeds a predetermined value, and the sum of the pixel increment values for the group can then be compared with a predetermined value. The pixel increment values for pixels in the group can first be summed for pixels in the same column, and then the sums for each column can be summed for the group. In this way the group of pixels can be moved one column at a time to carry out a group comparison for all pixels in a row. After detecting the existence of comb artifacts, they can be corrected by computing a function based on the values of pixels above and below the subject pixel. The correction can include blending the odd and even fields in a comb artifact area, e.g., giving one-quarter weight to the pixels above and below a subject pixel and xc2xd to the subject pixel. Alternatively, the correction can include removing one of the fields in the comb artifact and replacing the missing pixel by averaging the pixels immediately above and below it.
In another aspect, the invention features, in general, a system for correcting deinterlaced video that includes a comb artifact detector that receives deinterlaced video and determines whether the deinterlaced video has comb artifact areas, and an artifact corrector responsive to the detector to correct the comb artifact areas and produce corrected video.
In another aspect, the invention features, in general, a program storage media storing computer executable instructions that cause a computer to determine whether deinterlaced video has comb artifact areas, and correct the comb artifact areas.
Embodiments of the invention may include one or more of the following advantages. Comb artifacts are automatically and quickly detected and corrected in deinterlaced video.
Other advantages and features of the invention will be apparent from the following description of an embodiment thereof.